Rostanga arbutus is a species of sea slug, a dorid nudibranch, a marine gastropod mollusc in the family Discodorididae.

It was thought to be widely distributed, but this was due to confusion with other species.

[2] This dorid nudibranch is bright orange to reddish-orange in colour, and the dorsum is covered with caryophyllidia.

[2][3] This species is found mostly in the intertidal zone on the red sponge, Ophlitaspongia aceratoobtusa (family Microcionidae) on which it presumably feeds.

[2] Most other species of Rostanga also feed on sponges of the family Microcionidae.